Remove support for conflicting constructors.

sdk/lib/_internal/compiler/implementation/dart_backend/renamer.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart_backend;
 
 Function get _compareNodes =>
     compareBy((n) => n.getBeginToken().charOffset);
 
 typedef String _Renamer(Renamable renamable);
@@ skipping 91 matching lines @@
       }
     }
     return result.toString();
   }
 
   String renameConstructor(Element element, ConstructorPlaceholder placeholder,
       Function renameString, Function renameElement) {
     assert(element.isConstructor());
     StringBuffer result = new StringBuffer();
     String name = element.name.slowToString();
-    if (element.name != element.getEnclosingClass().name) {
+    if (element.name != const SourceString('')) {
       // Named constructor or factory. Is there a more reliable way to check
       // this case?
       if (!placeholder.isRedirectingCall) {
         result.write(renameType(placeholder.type, renameElement));
         result.write('.');
       }
-      String prefix = '${element.getEnclosingClass().name.slowToString()}\$';
-      if (!name.startsWith(prefix)) {
-        // Factory for another interface (that is going away soon).
-        compiler.internalErrorOnElement(element,
-            "Factory constructors for external interfaces are not supported.");
-      }
-      name = name.substring(prefix.length);
       if (!element.getLibrary().isPlatformLibrary) {
         name = renameString(element.getLibrary(), name);
       }
       result.write(name);
     } else {
       assert(!placeholder.isRedirectingCall);
       result.write(renameType(placeholder.type, renameElement));
     }
     return result.toString();
   }
@@ skipping 218 matching lines @@
     index ~/= firstCharAlphabet.length;
     int length = otherCharsAlphabet.length;
     while (index >= length) {
       resultBuilder.write(otherCharsAlphabet[index % length]);
       index ~/= length;
     }
     resultBuilder.write(otherCharsAlphabet[index]);
     return resultBuilder.toString();
   }
 }